The present invention relates to a method and an apparatus for applying adhesives to a surface, and more particularly, to a method and apparatus for reticulating an adhesive film to conform to a surface having a plurality of apertures therein, and most particularly, to a method and apparatus for reticulating an adhesive film to conform to the surface network formed by the edges of the cell walls of a honeycomb core.
A variety of methods and apparatus are employed in the prior art for applying adhesives to the surface network of a honeycomb core so that a surface or facing panel can be adhesively secured to the surface network of a honeycomb core to form one wall of a honeycomb panel. Such panels are employed in acoustical and structural applications. Among the methods presently used to apply an adhesive to a honeycomb core is one in which the edges of the honeycomb core are precoated with an adhesive prior to expanding the cells into a honeycomb network. This method is satisfactory for some uses, but for other uses does not allow a sufficient amount of adhesive to be applied, does not effect a uniform application of adhesive over the honeycomb core, and does not allow a bead of adhesive to be applied that extends over the edge of the walls of the honeycomb cells and down a very small distance onto the contiguous portion of the walls of the cells. Another method presently employed in the art is to apply the adhesive to the edges of a honeycomb core with an adhesive coated roller that is brought into rolling contact across the surface network of the core. This method is subject to the same disadvantages as adhesive application prior to expansion of the honeycomb cells, but in addition deposits an excess amount of adhesive onto the interior walls of the honeycomb cells.
Another method presently employed in the art for applying adhesives to the edge network of a honeycomb core is to overlay the surface network of a honeycomb core with a relatively thin sheet of thermosetting adhesive and thereafter to direct a hot airstream downwardly toward the surface of the adhesive causing the adhesive to shear or burst where it is unsupported by the surface network. This method, however, also deposits an excess amount of adhesive onto the interior walls of the honeycomb cells while leaving an insufficient amount of adhesive in the form of a bead on the surface network of the core.
Accordingly, it is a broad object of the present invention to provide a method and apparatus for applying an adhesive material to the surface of an article having a plurality of apertures therein and reticulating the adhesive to conform to the surface of the article, and more particularly, to provide a method and apparatus for reticulating an adhesive film to conform to the surface network of a honeycomb core. Additional objects of the present invention are to reduce the amount of adhesive required to form an adequate bead of adhesive on the surface of an apertured article adjacent the periphery of the apertures, and to form a bead that extends from the surface of the apertured article down a very small distance onto the interior walls of the apertures, so that, when a facing panel is contacted with the adhesively coated surface of the article, a small fillet of adhesive is formed between the interior surface of the facing panel and the interior walls of the apertures. It is a further object of the present invention to provide a method and apparatus for reticulating an adhesive onto the apertured surface of such an article so that an adequate bead is formed for bonding purposes, while requiring a lesser amount of adhesive than required by the prior art processes. It is a further object of the present invention to provide a method and apparatus whereby an adhesive film can be layed over the apertured surface of an article and thereafter reticulated to conform to the surface structure of the apertured article without depositing excess adhesive on the interior walls of the aperture. It is a further object of the present invention to provide a method and apparatus whereby a thin film of adhesive can be placed over the surface network of a honeycomb core and thereafter reticulated to expose the interior of the honeycomb cells, while forming a bead of adhesive on the edges of the honeycomb cells that extends a small distance into the cells along the cell walls contiguous the edges of the cell walls. It is a further object of the present invention to provide a method and apparatus that can be used to apply adhesives having improved strength and/or higher temperature resistance properties that could not be applied by prior art methods and apparatus. It is a further object of the present invention to provide a method and apparatus that can be employed with a wide range of adhesive compositions having a wide variety of melting and curing temperatures.